Valve device with relief action and suction action for hydraulic systems

ABSTRACT

The invention relates to a valve device intended for connection into a pressure fluid conduit, as for instance a pressure fluid conduit from a pressure fluid source to a hydraulic motor. The valve device has a combined relief or overpressure valve action and suction or underpressure valve action; at excessive pressure in the pressure fluid conduit pressure fluid being discharged through the valve device to a tank and at underpressure in the pressure fluid conduit a communication being established through the valve device between the pressure fluid conduit and a tank conduit for neutralization of the underpressure in the pressure fluid conduit. The valve device is easily adjustable to give alternatively only the overpressure valve action or only the underpressure valve action. A preferred embodiment of the valve device can be connected into two different pressure fluid conduits, as for instance the two pressure fluid conduits from a pressure fluid source to the two cylinder chambers of a double action hydraulic cylinder. This preferred embodiment of the valve device gives overpressure valve action as well as underpressure valve action in both pressure fluid conduits and can easily be adjusted to discharge the overflowing pressure fluid at an excessive pressure in any one of the pressure fluid conduits alternatively to a tank conduit or directly to the other pressure fluid conduit.

United States Patent 72] Inventor Stig Gote Stenlund Boras, Sweden [21 Appl. No. 839,207 [22] Filed July 7, 1969 [45] Patented Jan. 12, I971 [73] Assignee Monsun-Tison AB Boras, Sweden 2 company of Sweden [32] Priority July 11, I968 [33] 1 Sweden [31] 9567 [54] VALVE DEVICE WITH RELIEF ACTION AND SUCTION ACTION FOR HYDRAULIC SYSTEMS 9 Claims, 6 Drawing Figs.

' [52] U.S. Cl 137/270, 137/493. 6, 137/512.5 [51] Int. Cl. Fl6k 17/18 [50] Field of Search 137/270, 271, 269.5, 270.5, 269, 512.5, 493.6, 493.3, 493.7, 493.9

[56] References Cited UNITED STATES PATENTS 1,229,885 6/1917 Chadwick 137/4 93.6X 2,393,589 1/1946 Compton et a1. 137/493.6X 1,497,063 6/1924 Brehmer 137/493.6X 10/ l 954 Orchowski 137/493.6X

Primary Examiner-M. Cary Nelson Assistant ExaminerRobert J. Miller Anorney Waters, Roditi, Schwartz & Nissen ABSTRACT: The invention relates to a valve device intended for connection into a pressure fluid conduit, as for instance a pressure fluid conduit from a pressure fluid source to a hydraulic motor. The valve device has a combined relief or overpressure valve action and suction or underpressure valve action; at excessive pressure in the pressure fluid conduit pressure fluid being discharged through the valve device to a tank and at underpressure in the pressure fluid conduit a communication being established through the valve device between the pressure fluid conduit and a tank conduit for neutralization of the underpressure in the pressure fluid conduit. The valve device is easily adjustable to give alternatively only the overpressure valve action or only the underpressure valve action. A preferred embodiment of the valve device can be connected into two different pressure fluid conduits, as for instance the two pressurefluid conduits from a pressure fluid source to the two cylinder chambers of a double action hydraulic cylinder. This preferred embodiment of the valve device gives overpressure valve action as well as underpressure valve action in both pressure fluid conduits and can easily be adjusted to discharge the overflowing pressure fluid at an excessive pressure in any one of the pressure fluid conduits alternatively to a tank conduit or directly to the other pressure fluid conduit.

SHEET 3 [if 6 Fig.3

PATENTEU JAN 1 2 mm SHEET 5 [1F 6 Fig.5

particular a valve device of this type intended'to be connected a members in their associated bores. With such a valve device to or inserted in one'or both 'of the vpressure fluid conduits to a hydraulic motor, forinstance a hydraulic cylinder, driven from a pressure fluidsupply.

'The object of the invention is to providea valve device of this type which is easily adjustable to give difierent desired flow combinations in a 'hydraulic system in which the valve device is inserted. f q A more specific object o'f the'invention is therefore to provide a valve device which ca'rrbe connected to or inserted in the'pressnre fluidc'ond'uits to a hydraulicmotor and which in- I eludes for at least oneof these pressure fluidconduitsor for both of them a pressure limiting or relief valve, which opens for discharging pressure fluid from "the connected fluid pres-. sure conduit at excessive 'pressure or overpressure in this conduit, as well as asuction valve, which opens ata 'too low pressure or underpressure in the connected'pressureffluid conduit for equalization -of this underpressurein particular, itis the object of the'invention to provide a valve device of this type, the operation of which, is easilyselectable so that the relief valve can discharge pressure fluid atexcessive pressure or overpressure in the connected pressure fluid conduit either to a tank conduit or to the other pressure fluid conduit for the same hydraulic motor. i l

According tothe invention these and further objects are obtained by a valve device comprising a valve body with at least a first longitudinal boreandfirst and 'secondsta'tionary valve seats at opposite ends of said bore, a first valve member disposedin said bore between said first andsecondvalve seats and provided with a first'and a second valve cone located at;

opposite ends of i said valve member facing in opposite directions for cooperating with said first and second stationary valve seats respectively and with forceexerting means urging said valve cones into'sealing'relationship with said'valve seats, said valve member permitting a fluid flow in said longitudinal bore between said first and second stationary valve seats, at

least a first fluid chamberin said. valve body located at one end of said longitudinal bore'so as to communicate with said bore 7 via one of s'aid'stationary valve seats, said valve member being provided with relief valve means at the end of the valve member closest to said firstfluid chamber for opening at a fluid pressure in said bore exceeding a predetermined value to establish communication between said bore and said first fluid chamber, and said valve body being provijdedjwith a first pressure fluid port communicating with said longitudinal between said first and second valve seats and adapted to be connected to a pressure fluid conduit and a first tankport communicating their associated stationary valve seats respectively are so dimensioned that each valve member can be mounted in its as sociated' bore facing alternatively in the'one or in the opposite or reversed direction. 7 v I With a valve device according to this preferred'embodiment 7O 7 of the invention itis possible to obtaina large number of different operations of the valve device by. mounting a valve member only in one of the valve bores while sealing the open end ofthe other bore or' by mounting valve members in both with said first fluid chaniber'and adapted to be connected toa' connected to the two fluid pressure conduits to a hydraulic motor, as for instance a hydraulic cylinder, and to a tank conduit it is possible for instance to obtain following different operations of the valve device:

a. With a valve member mounter only in the one bore and theother bore sealed the valve device functions as a relief or overpressure valve and at the same time as-a suction or underpressure valve for only the one motor connection and with the relief valve discharging the-fluid to the tank conduit at excessive pressure or overpressure in the motor connectiomthis operation be obtainable for either one of the motor connections by mounting the valve member in the oneor the-other bore;

With valve members mounted in both bores the valve device can dependent on the mounting direction of the valve members in their associated bores operate as: 1. ,A relief valve and at the same time asuction valve in .both motor connections, the overflowing fluid being discharged to the tank conduit at excessive overpressure in the-motor connections;

2. a so-called cross-over or double" safety valve, which at excessive pressure or overpressure in anyone of the motor-connections discharges the overflowing fluid directly tothe other motor connection, and at the same time asa suction valve for both motor connections. or v 3. a mixed" relief valve, which at excessive or overpressure in the one motor connection discharges the overflowing fluid directly to the other motor connection, whereas at excessive pressure or overpressure in said other motor connection the overflowing fluid is discharged to the tank conduit, and at the same time as asuction valve .for'both motor connections. The valve member or valve members of a valve device according to the invention can also easily be-designed so as to be adjustable to give only relief valve action or alternatively only suction valve action. a

' All'these various operations are obtainable with one or two 'valve membersmounted inacommon valve body, the desired the one bore whereas the'other bore is sealed;

"FIG. 2 shows the same valve device as in FIG. I but with valve members mounted in both bores in the opposite or reversed direction ascompared with in' the valve device in FIG. 1;

FIG. 3'is a hydraulic circuit diagram for a valve device of the single valve member I the type. illustrated in FIGS. I and'Zconnected to the pressure I the valve members'with their-valve-conesand the bores with '65 fluid conduits to a hydraulic motor and adjustedto give the type of operation described in point (a) in the foregoing;

FIG. 4 is a hydraulic circuit diagram for the same valve device adjusted to give the type of operation described in point (bl in'the foregoing;

' FIG. 5 is a hydraulic'circuit forthesame valve device ad justedto give thetype ofoperation described in point(b2) in the foregoing; and

FIGJ6 is a hydraulic circuit diagram for'the same valve :deviceadjusted to give the type of operation described in (b3 in the foregoing;

F'lGcI shows a valve device according to the invention-comprising a valve body I provided with two identical longitudinal bores-land 3, each adapted to receive a valve member. For

i I each one of the bores 2 and 3 respectively the valve body I is provided with a pressure fluid flow 'passage 4 and 5"resp'ective- -ly, which communicates with the associated bore and passes bores and by reversingthe mounting direction of the valve through the valve'body'l and is adapted to be connectedinto a pressure fluid conduit from a direction control valve (not shown in the drawing) to the one actuating chamber of a hydraulic motor, for instance the one cylinder chamber of a hydraulic cylinder (not shown in the drawing). For each bore 2 and 3 respectively the valve body 1 is also provided with an outlet or tank port 6 and 7 respectively adapted to be connected for instance to a tank conduit. The bores 2 and 3 communicate with each other at their bottom ends through a flow passage 8 in the valve body 1.

In the valve device according to the invention illustrated in FIG. 1 a valve member is mounted only in the one bore 2, whereas the other bore 3 is sealed with a plug 30 having a narrow waist 31 permitting a fluid flow through the flow passage adapted to be connected into a pressure fluid conduit. The plug 30 is also provided with an internal flow passage 32 establishing a communication between the inner end -of the' bore 3 and the outlet port 7, which is adapted to be connected to a tank.

The valve member according to the invention mounted in the bore 2 is provided with two valve cones 9 and 13 respectively located at opposite ends of the valve member so as to face in opposite direction. The valve cone 13 is integral with the main potion 11 of the valve member, whereas the valve cone 9 is axially movable relative to the main portion 11 of the valve member. A coil spring 10 acting between the valve cone 9 and the main portion 11 of the valve member urges the valve cone 9 and the valve cone 13 in opposite directions, that is away from each other. The valve cone 9 is urged into sealing relationship with a stationary valve seat 12 at the bottom end of the bore 2 between the bore and the flow passage 8, whereas the other valve cone 13 at the opposite end of the valve member is urged into sealing relationship with a stationary valve seat 14. This valve seat is provided in a plug 15 which is screwed into the open end of the bore 2 and which is provided with a recess 16 communicating with the outlet port 6 of the valve body 1 and having an annular rim forming the stationary valve seat 14 cooperating with the valve cone 13.

The valve formed by the cooperating valve cone l3 and valve seat 14 is consequently located between the outlet port 6, which is adapted to be connected to a tank conduit, and the bore 2, which communicates with the flow passage 4 adapted to be connected into a pressure fluid conduit. The main portion 11 of the valve member is provided with longitudinal grooves or flow passages 26 in its circumference permitting a fluid flow within the bore 2 along the valve member between the valve seat 14 at the outer end of the bore 2 and the valve seat 12 at the bottom end of the bore. Consequently, the valve formed by the cooperating valve cone 9 and valve seat 12 is located between the flow passage 4 adapted to be connected into the pressure fluid conduit and the flow passage 8, which communicates via the other bore 3 and the passage 32 in the sealing plug 30 with the outlet port 7, which is also adapted to be connected to a tank conduit.

Further, the valve member is provided with a relief or overpressure valve located in the valve cone 13. This relief valve consists of an annular valve seat 17 provided in the valve cone 13 and a valve disc 18 cooperating with said valve seat 17. The valve disc 18 is attached to the one end of a valve rod 19 axially movable in the main portion 11 of the valve member and is urged into sealing relationship with the valve seat 17 by a biassing coil spring 20 acting against a washer 21 mounted on the valve rod 19. The valve rod 19 has a reduced portion 22 located in a cavity 23 in the valve cone 13. This cavity 23 communicates through radial openings 24 with the bore 2 and thus with the pressure fluid flow passage 4. Thus, the cooperating valve seat 17 and valve disc 18 form a relief or overpressure valve, which is located between the flow passage 4 and the outlet port 6 and which opens at an excessive pressure in the flow passage 4 determined by the difference in cross-sectional area between the valve rod 19 and the opening surrounded by the valve seat 17 and by the biassing force of the coil spring 20.

The valve device according to the invention shown in FIG. l operates as a relief or overpressure valve in the following manner: The pressure in the pressure fluid conduit which is connected to the flow passage 4 and thus communicates with the cavity 23 in the valve cone 13 acts against the backside of the valve disc 18. When this pressure exceeds the biassing force of the coil spring 20, the valve disc 18 is lifted from its seat 17 in the valve cone [3 ofthe main portion 11 of the valve member, whereby the overflowing pressure fluid is discharged into the recess 16 in the plug 15 and thus to the outlet port 6 which is connected to a tank conduit. In order to secure a reliable operation of this type, if there should not exist a communication to the tank from both ends ofthe valve member as the case is in the valve device illustrated in FIG. 1. that is if the valve body 1 should be provided with only one bore 2 having a closed bottom end instead of the communication passage 8 or if the sealing plug 30 screwed into the open end of the other bore 3 should not be provided with the communication passage 32 to the outlet port 7, the valve member is provided with an axial bore 25 extending through the valve disc 18 and its valve rod 19. Through this axial bore 25 any pressure fluid leaking past the sealing between the valve cone 9 and the associated valve seat 12 can flow to the tank through the outlet port 6. Thanks to this longitudinal bore 25, which forms a restricted flow path between the spaces in the valve body located at opposite ends of the valve member, it is secured that tank conduit pressure is present at both ends of the valve member, whereby a'reliable operation of the valve device is guaranteed under all conditions.

As a suction or underpressure valve the valve device illustrated in FIG. 1 operates in the following way: If the fluid pressure in the pressure fluid conduit which is connected to the flow passage 4 and thus to the bore 2 falls below the fluid pressure in the tank conduit connected to the outlet ports 6 and 7, the fluid pressure in the tank conduit acting upon the two end surfaces of the valve member, on the one hand in the recess 16 in the plug 15 and on the other hand in the fluid passage 8 between the two bores 2 and 3, will overcome the biassing force of the coil spring 10, whereby the entire valve member is compressed and shortened. Thereby the valve cone 13 will be lifted from its associated seat 14 and/or the valve cone 9 be lifted from its associated seat 12 so that a communication is established from the outlet port 6 through the valve 13,14 and/or from the outlet port 7 through the valve 9,12 to the flow passage 4 connected to the pressure fluid conduit, whereby the prevailing underpressure in this pressure fluid conduit is neutralized. It is appreciated that this suction valve action is obtained even if, as mentioned above, the valve body 1 is provided with only one bore 2 or the sealing plug 30 screwed into the other bore 3 does not have the communication passage 32 to the outlet port 7.

It is also appreciated that the valve device can easily be adjusted to operate only as a relief valve, if the coil spring 10 is tightened to be fully compressed, for instance by the aid of additional washers, or alternatively to operate only as a suction valve, if the coil spring 20 is tightened to be fully compressed.

it is also appreciated that the valve device illustrated in FIG. 1 can easily be modified to operate as a combined relief valve and suction valve for both of the pressure fluid conduits connected to the flow passages 4 and 5 in the valve body, as for instance the pressure fluid conduits to the two cylinder chambers of a hydraulic cylinder, in that an additional second valve member is mounted also in the other bore 3 in exactly the same way as the valve member positioned in the bore 2.

In certain closed hydraulic systems, however, it is not desired that the relief valve discharges the overflowing pressure fluid to a tank at an excessive pressure in a pressure fluid conduit but that the overflowing pressure fluid is instead discharged directly from the pressure fluid conduit with excessive pressure to another pressure fluid conduit, for instance to the pressure fluid conduit connected to the other cylinder chamber of the same hydraulic motor. Such an operation can readily be obtained with the valve device according to the invention illustrated in FIG 1 in that valve members are mounted in both bores 2 and 3 but in the opposite or reversed direction as compared to FIG. lso that the valve members positioned in the twobores 2 and 3 have their valve cones 13 provided with the relief valves 17,18 facing the' communication passage 8 between the bores.

FIG. 2 in the'ac'companying'drawing illustrates the valve device modified in this way, the various parts of the valve member mounted in the bore3 and all other details associated with this bore being provided with the same reference characters as the corresponding parts or details: in the bore. 2 followed by a prime sign. Consequently, in'this valve device according tothe invention the valve members are inserted or mounted intheir associated bores 2 and 3 so as to have their relief valve discs 18 and 18 respectively facing each other, the

valve cones 13 and 13" respectively cooperatingwith the sta- I tionary valve seats 12 and.12.' at the communication passageB between the bottom ends of the bores 2 and 3 and the valve cones Q and 9' respectively cooperating with the stationary valve seats Hand .14 respectivelyin the plugs and 15' respectively screwed into the openends of the bores. If the fluid pressurein either one of the pressure fluid conduits, connected to the flow passages 4 and 5 in the valve body 1 should exceed the preset opening pressure for the relief valve of the valve member mounted in the associated bore 2 or 3respectively, this relief valve will open as described in the foregoing and establish a communication from the pressure fluid conduit having the excessive pressure (4 or 5) to the flow passage 8 between the two bores 2 and 3.- The valvecmember-mounted in the other bore (on the low-pressure side) willthen be compressed'against the action of the biassing spring l0'so that the pressure fluid from the high-pressure side in the flow passage 8 can discharge directly into the other pressure, fluid conduit (4 or 5) through the longitudinal grooves orpassages. 26in the main portion of said 'valve member. Thus, the overflowing pressure fluidat an excessive pressureineither one of the pressure fluid connections 4 and 5 is not discharged to the tank but directly to the other pressure fluid connection. Should a too low pressureor underpressu re appear in either one of the pressure fluid connections 4 and 5, the valve device will operate as a suction valve in the manner described in the foregoing with reference to FIG. I so that a communication is.

establishedbetween thepressurefluid-conduit having the too low pressureand the associated tank connection 6 or 7 for neutralization of the-uhderpressure.

FIG. 3 is a hydraulic circuit diagram for a hydraulic system including a valve device according to the invention designed as illustrated in FIG. l-and adjusted tooperate as a combined relief valve and suction valve onlyfor the one pressure fluid conduit to a hydraulic cylinder. The valve' device according to the invention is schematically illustrated within the frame V; the relief or overpressure valve 17, 18 withits associated biassing spring being illustrated by the symbol 50, the valve formed by the cooperating valve cone 13 and valve seat 14 being illustrated by the symbol 51, the valve formed by the cooperating valve cone 9 and valve seat 12 being illustrated by the symbol 52 and the restricted flow passage'v25 by the symbol 53-. The relief or overpressure valve 50 is consequently connected to the one pressure fluid conduit M1 to the hydrau; lic cylinder M, whereas the other pressure fluid conduit'MZto the other cylinder chamber of the hydraulic cylinder M has no relief l/alve or suction valve connected to it. The pressure flu id conduits M1 and M2 for. the hydraulic cylinder M are, conhas a communication with the tank 56 only through the longitudinal bore forming the flow restriction 53.

FIG. 4 is a hydraulic circuit diagram for a valve device according to FIG. 1 but with valve members mounted in both bores 2 and 3 with the direction illustrated in FIG. 1, that is with the valve cones 9 of the two valve members facing each other. In this case consequently, the valve device is connected into both pressure fluid conduits M1 and M2 to both cylinder chambers of the hydraulic cylinder M and will operate as a relief or overpressure valve and at the same time as a suction valve in both pressure fluid conduits to the hydraulic motor M, the overflowing pressure fluid. at an excessive pressure in anyone of these pressure fluid conduits beingdischarged to the tank '56. The valve device has consequently an operation as described under (blin the foregoing. The connection designated with 57 in the circuit diagram in FIG. 4 consists of the communication passage 8 between the two bores 2 and 3.

The valve functions of the valve member mounted in the bore 3 are provided with the same reference characters as the valve functions of the valve member mounted in the bore 2 but folnecte to a control device 'consisting of a direction control 7 valve 54, which in turn is connected to a pressurefluid pump 55 and a tank. 56. The tank 56 is also connected to the discharge end of the relief valve 50and tothe suction valves 51 a d 52 in the valve device according to the invention. It sho ld be notedthat in the circuit diagram in FIG. 3 it has bee assumed that the sealing'plug 30 screwed into the bore3 4 in t e valve device illustrated in FIG/I is not provided with the onmunication.passage. 32, wherefore the suction valve 52 f rmed by the cooperating valve cone 9 and valve seat 12 lowed by a prime sign.

FIG. 5 illustrates the circuit diagram for a valve device designed as illustrated in FIG. 2'and connected into bothpressure fluid conduits to the hydraulic cylinder. In this case consequently the valve device will operate as a so-called cross over safety valve with suction valve action for both pressure fluid conduits to the hydraulic motor as described under (b2) in the foregoing. As in thiscase the two valve members are mounted in their associated bores in the manner illustrated in FIG. 2, it should be noted that the suction valve 51 is formed by the valve cone 13 and the valveseat l2 and that the suction valve 52 is formed by the valve cone 9'and the valve seat 14 and correspondingly for the suction valves 51' and 52 formed by the other valve member mounted in the other bore of the valve body.

FIG. 6 illustrates the hydraulic circuit diagram'for a valve device according to the invention having a valve body as illustrated in FIGS. 1 and 2 and provided with valve members in both bores 2 and 3 and connected to the two pressure fluid conduits M1 and M2 to ahydrauliccylinder M. In this case, however, the valve member in the bore connected to the pres sure fluid conduit Mlis mounted in the position shown in FIG. 2 with the relief valve facing the communication passage 8. whereasrthevalve member in the bore. 3 connected to the pressure fluid'conduit M2 is mounted in the position illustrated in FIG. I with the valve cone 9 facing the communication passage 8. Thus, the suction valve 52 is in this case formed by the cooperating valve cone 9 andvalve seat 14, the suction valve 51 by the cooperatingvalve cone 13 and valve seat12, the suction valve 52' by the cooperating valve cone 9' and valve seat 12 in the bore 3 and the suction valve 51 by the cooperatingvalve cone 13' and valve seat 14'. in the bore. 3. Consequently, the valve device will in this case have-an: operation as described in (b3) in the foregoing, whereby the overflowing pressure fluid at an excessive pressure in-thepres-N sure fluid conduit M1 is discharged directly to the other pressure fluid conduit M2 whereas the overflowing pressure fluid at an excessive'pressure inthe pressure fluid conduit M2 ,is

discharged to the tank 56. At an underp'ressure in either one axial fluid flow in said first bore between said first and second stationary valve seat, said first valve member including flrst and second valle cones (9,13) facing in opposite directions at opposite ends L first and second stationary valve seats respectively, said; first and second valve cones being mutually axially movable. and

force exerting? means (10) acting between said first, and

f said valve member for cooperating with said second valve cones for urging them into sealing relationship with said first and second valve seats respectively, a first fluid chamber (16) located at the one end of said first longitudinal bore so as to communicate therewith via one of said stationary valve seats (14), said first valve member also including an overpressure valve (17,18) provided in the end of the valve member closest to said first fluid chamber for opening and establishing communication between said first bore (2) and said first fluid chamber (16) when the fluid pressure in said bore exceeds a predetermined value, a first pressure fluid port (4) in said valve body (1) communicating with said first bore 2) between said first and second valve seats and adapted to be connected to a pressure fluid conduit, and a first outlet port (6) in said valve body (1) communicating with said first fluid chamber (16) and adapted to be connected to a tank conduit.

2. A valve device as claimed in claim 1, wherein a second fluid chamber (8) is provided in said valve body (1) at the other end of said first longitudinal bore (2) so as to communicate therewith via the other one of said stationary valve seats (12) and said first valve member is provided with an axial bore (25) extending from the one end to the opposite end of the valve member and forming a flow passage between said first and second fluid chambers (16,8).

3. A valve device as claimed in claim 2, wherein said first bore (2) has a bottom end provided with said second stationary valve seat l2) and communicating with said second fluid chamber (8) and an open end, a plug (15) being inserted in said open end of said first bore, said plug including said first fluid chamber (16) and being provided with said first stationary valve seat (14) between said first fluid chamber and said first bore.

4. A valve device as claimed in claim 1, wherein said valve body (1) includes a second fluid chamber (8) located at the other end of said first bore (2) so as to communicate therewith via the other stationary valve seat (12), and a second outlet port (7) communicating with said second fluid chamber (8) and adapted to be connected to a tank conduit.

5. A valve device as claimed in claim 1, wherein said first and second stationary valve seats (12,14) have the same shape and size and said first and second valve cones (9,13) on said first valve member have also the same shape and device, whereby the valve member can be selectively mounted in said first bore in anyone of two mutually reversed positions.

6. A valve device as claimed in claim 1, wherein said valve body (1) has a second longitudinal bore (3) similar to said first longitudinal bore (2) with third and fourth stationary valve seats (14', 12) at opposite ends of said second bore; a second valve member similar to said first valve member being mounted in said second bore for cooperation with said third and fourth stationary valve seats; the valve body including also a second fluid chamber (8) communicating with said first and second bores (2,3) via said second and fourth stationary valve seats (12,12') respectively, a third fluid chamber (16') communicating with said second bore (3) via said third stationary valve seat (14' a second pressure fluid port (5) communicating with said second bore (3) between said third and fourth valve seats and adapted to be connected to a pressure fluid conduit, and a second outlet port (7) communicating with said third fluid chamber (16') and'adapted to be connected to a tank.

7. A valve device as claimed in claim 6. wherein said stationary valve seat (12,14,12',14) have the same shape and size and said first and second valve cones (9,13,9'.13') on said first and second valve members respectively also have the same shape and size, whereby each of said valve members can be mounted selectively in any one of two mutually reversed positions in its associated bore.

8. A valve device as claimed in claim 1, wherein the minimum axial spacing between said first and second valve cones (9,13) of said first valve member corresponds to the axial spacing between said first and second stationary valve seats (14,12) so that said valve cones cannot be lifted from their associated stationa valve seats. I

9. A valve device as c armed in claim 1, wherein said first valve member includes biassing means (20) for said relief valve (17,18) for determining the opening pressure of said relief valve, said biassing means (20) being adjustable to main tain said overpressure valve (17) closed against any overpressure. 

1. A valve device comprising a valve body (1) having at least a first longitudinal bore (2) and first and second stationary valve seats (12,14) at opposite ends of said bore, a first valve member mounted in said first bore and permitting an axial fluid flow in said first bore between said first and second stationary valve seat, said first valve member including first and second valve cones (9,13) facing in opposite directions at opposite ends of said valve member for cooperating with said first and second stationary valve seats respectively, said first and second valve cones being mutually axially movable, and force exerting means (10) acting between said first and second valve cones for urging them into sealing relationship with said first and second valve seats respectively, a first fluid chamber (16) located at the one end of said first longitudinal bore so as to communicate therewith via one oF said stationary valve seats (14), said first valve member also including an overpressure valve (17,18) provided in the end of the valve member closest to said first fluid chamber for opening and establishing communication between said first bore (2) and said first fluid chamber (16) when the fluid pressure in said bore exceeds a predetermined value, a first pressure fluid port (4) in said valve body (1) communicating with said first bore (2) between said first and second valve seats and adapted to be connected to a pressure fluid conduit, and a first outlet port (6) in said valve body (1) communicating with said first fluid chamber (16) and adapted to be connected to a tank conduit.
 2. A valve device as claimed in claim 1, wherein a second fluid chamber (8) is provided in said valve body (1) at the other end of said first longitudinal bore (2) so as to communicate therewith via the other one of said stationary valve seats (12) and said first valve member is provided with an axial bore (25) extending from the one end to the opposite end of the valve member and forming a flow passage between said first and second fluid chambers (16,8).
 3. A valve device as claimed in claim 2, wherein said first bore (2) has a bottom end provided with said second stationary valve seat (12) and communicating with said second fluid chamber (8) and an open end, a plug (15) being inserted in said open end of said first bore, said plug including said first fluid chamber (16) and being provided with said first stationary valve seat (14) between said first fluid chamber and said first bore.
 4. A valve device as claimed in claim 1, wherein said valve body (1) includes a second fluid chamber (8) located at the other end of said first bore (2) so as to communicate therewith via the other stationary valve seat (12), and a second outlet port (7) communicating with said second fluid chamber (8) and adapted to be connected to a tank conduit.
 5. A valve device as claimed in claim 1, wherein said first and second stationary valve seats (12,14) have the same shape and size and said first and second valve cones (9,13) on said first valve member have also the same shape and device, whereby the valve member can be selectively mounted in said first bore in anyone of two mutually reversed positions.
 6. A valve device as claimed in claim 1, wherein said valve body (1) has a second longitudinal bore (3) similar to said first longitudinal bore (2) with third and fourth stationary valve seats (14'', 12'') at opposite ends of said second bore; a second valve member similar to said first valve member being mounted in said second bore for cooperation with said third and fourth stationary valve seats; the valve body including also a second fluid chamber (8) communicating with said first and second bores (2,3) via said second and fourth stationary valve seats (12,12'') respectively, a third fluid chamber (16'') communicating with said second bore (3) via said third stationary valve seat (14''), a second pressure fluid port (5) communicating with said second bore (3) between said third and fourth valve seats and adapted to be connected to a pressure fluid conduit, and a second outlet port (7) communicating with said third fluid chamber (16'') and adapted to be connected to a tank.
 7. A valve device as claimed in claim 6, wherein said stationary valve seat (12,14,12'',14'') have the same shape and size and said first and second valve cones (9,13,9'',13'') on said first and second valve members respectively also have the same shape and size, whereby each of said valve members can be mounted selectively in any one of two mutually reversed positions in its associated bore.
 8. A valve device as claimed in claim 1, wherein the minimum axial spacing between said first and second valve cones (9,13) of said first valve member corresponds to the axial spacing between said first and second stationary valve seats (14,12) so that said valve cones cannot be lifted from their associated stationary Valve seats.
 9. A valve device as claimed in claim 1, wherein said first valve member includes biassing means (20) for said relief valve (17,18) for determining the opening pressure of said relief valve, said biassing means (20) being adjustable to maintain said overpressure valve (17) closed against any overpressure. 